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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
365963
2Even Fibonacci numbers
302493
3Largest prime factor
221005
4Largest palindrome product
201237
5Smallest multiple
214781
6Sum square difference
216422
710001st prime
185350
8Largest product in a series
164634
9Special Pythagorean triplet
162449
10Summation of primes
148787
11Largest product in a grid
111999
12Highly divisible triangular number
101237
13Large sum
107798
14Longest Collatz sequence
105707
15Lattice paths
87987
16Power digit sum
110534
17Number letter counts
72737
18Maximum path sum I
71311
19Counting Sundays
65784
20Factorial digit sum
100909
21Amicable numbers
70730
22Names scores
66027
23Non-abundant sums
49665
24Lexicographic permutations
57162
251000-digit Fibonacci number
77315
26Reciprocal cycles
40714
27Quadratic primes
42929
28Number spiral diagonals
57011
29Distinct powers
51456
30Digit fifth powers
54742
31Coin sums
40443
32Pandigital products
34827
33Digit canceling fractions
35959
34Digit factorials
47792
35Circular primes
43692
36Double-base palindromes
46483
37Truncatable primes
36961
38Pandigital multiples
31396
39Integer right triangles
36345
40Champernowne's constant
40722
41Pandigital prime
34049
42Coded triangle numbers
39027
43Sub-string divisibility
28922
44Pentagon numbers
27873
45Triangular, pentagonal, and hexagonal
37018
46Goldbach's other conjecture
29657
47Distinct primes factors
28501
48Self powers
61698
49Prime permutations
28205
50Consecutive prime sum
30371